Background: Irukandji syndrome definition is still widely misunderstood. Irukandji-like syndrome is more unclear than Irukandji syndrome. This study aimed to describe Irukandji-like syndrome in cases involving stinging by single-tentacle box jellyfish species in Thailand.

Materials and methods: Surveillance system and networks of toxic jellyfish incidents were established to enable case detection. In the period 2007 to 2019, all cases of stinging by single-tentacle box jellyfish resulting in collapse, hospital attendance or death were investigated.

Results: The majority of the 19 Irukandji-like syndrome cases were male (68.2%), median age 35.0 years (range 6.0–60.0), and Thai nationality (52.3%). Clinical manifestations of Irukandji-like syndrome were categorised as severe wound pain with immediate systemic reaction (66.7%), moderate wound pain with gradual systemic reaction (16.7%), and moderate wound pain with the immediate systemic reaction after a physical/chemical trigger (16.7%). The pain occurring when being stung differed from the pain occurring during the systemic reaction. The five most common symptoms were pain (100.0%), high blood pressure (100.0%), palpitations (86.7%), respiratory distress (52.6%), and near collapse/collapse (31.6%). The pain occurs when being stung was excruciating or burning pain at the wounds, felt like an electric shock, and rapidly expanded to heart pain. While the pain occurring during the systemic reaction was back pain, muscle pain, joint pain, abdominal pain, and body aches. The marks from the tentacles appeared similar in appearance to the caterpillar tracks of tanks. In 6 cases the species could be identified and all of them involving the Morbakka spp.

Conclusions: This was the largest study of Irukandji-like syndrome cases involving stings by single-tentacle box jellyfish in Thailand and the different clinical manifestations might be caused by different species of single-tentacle box jellyfish.